There are two categories of IVF failure: Problems with the embryo and problems with the carrier.
Today on InfertilityTV we are going to discuss problems with the embryo.
Problems with embryos make up the majority of IVF failures after embryo transfer,
Unfortunately there is one inescapable fact. Most embryos that
are produced by human beings are not capable of ever producing a live born baby.
The science behind that statement is very clear: Humans are inefficient at reproduction
Primarily because we produce a lot of abnormal embryos
There are lots of different ways in which embryos can be abnormal
As IVF specialists, there are some types of abnormalities that we can detect and
and others that we can't. The easiest abnormalities to detect are those that
can be seen under a microscope. After fertilization, some embryos will not
start dividing. Other embryos might divide for a few days and then stop.
This is called embryonic arrest
An arrested embryo should be easily detectable,
but some IVF programs will transfer an embryo too quickly so that it is
impossible to determine if it is developing.
This is the main reason why
day 3 embryo transfers do not result in pregnancy as often as day 5 or 6 transfers
Programs that put embryos into the uterus after only 2 or 3 days are
often going to be transferring arrested embryos that have no ability to produce
a pregnancy
Not all embryos stop developing completely.
Some embryos may be dividing but are doing it very slowly
We know, for example, that embryos that
are healthy and viable should reach certain stages of development at certain times.
Embryos that are slow, that don't reach these milestones when they are supposed to
have a lower chance for pregnancy
In many cases, these are problems that cannot be fixed.
These are still considered abnormal embryos
but these abnormalities are not as severe and so sometimes these
embryos may still be able to develop and implant into the uterus
Next. There are embryos that are dividing and doing so at the rate we expect but which look
abnormal under the microscope
Sometimes, they can look dark or show
lots of cells that are fragmented.
Skilled embryologists can also detect
abnormalities within the cells that indicate an embryo with a poor potential
for pregnancy
Now, everything we've talked about so far can be detected
using a microscope there are some embryos that look perfect under the
microscope but have other kinds of abnormalities.
The most common type of abnormality
are embryos which don't have the correct number of chromosomes.
A healthy normal embryo has 46 chromosomes 23 that come from the father and 23 from the mother.
It is extremely common for humans to have embryos with too many or
too few chromosomes
We do have technology to detect these abnormalities
Watch this playlist if you are interested in learning more about
pre-implantation chromosome testing
We do not have technology that will prevent
embryos with chromosome abnormalities nor do we have technology which can fix embryos.
As women get older they produce more and more embryos with chromosome
abnormalities and less normal embryos.
Sometimes, you just have to get lucky to
find a normal embryo that is why creating many embryos is a big advantage
when doing IVF
Now, some embryos have the correct number of chromosomes,
but the chromosomes themselves are abnormal in some way
Sometimes chromosomes can have a missing chunk these are called deletions.
Sometimes they can have an extra piece called a duplication
Many of these abnormalities can be detected
with current pre-implantation testing technologies
And again. These problems cannot be prevented or fixed!!
The strategy is to identify these abnormalities and dispose of those
embryos rather than transfer them
Remember, chromosomes are the part of the
cell which contains genetic information
Even though there are only 23 different chromosomes,
they contain tens of thousands of individual genes.
Each of those genes does something. Some genes are responsible for causing the embryo to divide,
Other genes control its ability to implant in the uterus and
others control the development of the fetus and its organs.
Just like there can be problems with chromosomes
there can also be problems with individual genes
These are called gene mutations.
We know lots of gene mutations that can cause disease in humans.
We can even test people or embryos for those mutations.
We also suspect that there are gene mutations that will prevent an embryo
from producing a viable pregnancy.
Even though we have the technology to test
for genetic mutations in embryos we don't yet know which genes to test
Remember, there are tens of thousands of them
So you see, even when your IVF doctor tells you
your embryos looked perfect before your embryo transfer
The great likelihood is that most of the time it is an abnormal embryo that has
no chance to produce a pregnancy
In the future, we will undoubtedly have newer technologies
that will allow us to identify more and more abnormal embryos
But for now we are going to be stuck transferring these embryos and keeping
our fingers crossed that they are normal enough to produce a healthy pregnancy.
If you are interested in learning more about chromosome testing of embryos like
I talked about earlier in this video
click the video on the left
If you want to become a patient at IVF1 click the link in the description
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